Currently, there are a number of techniques used to seal the valves in inflatable bodies. The most common technique in lighter-than-air helium filled balloons is to use a valve that relies on the internal pressure of the inflated body and the molecular attraction of certain plastic film materials to achieve a seal.
Gregory U.S. Pat. No. 1,008,641 discloses a self-sealing valve in a balloon comprising a generally flat tube extending through and sealed to the wall of the balloon with the sides of the flat tube remaining in contact to form a seal except when they are forcibly separated.
Davenport U.S. Pat. No. 2,597,924 discloses a self-sealing valve in a bladder comprising a pair of layers of plastic sheet material which relies on the internal plastic and the molecular adhesion of the material to form the seal. While these prior attempts have been successful to some degree, they still allow an unacceptably high rate of leakage particularly when used with lighter than air gases such as helium which gas tends to leak through microscopic openings.